The spine or vertebral column comprises a plurality of separate vertebrae. The vertebrae are movable relative to one another, and separated from one another by fibrocartilage called intervertebral discs.
In its entirety, the spinal column is highly complex in that it houses and protects critical elements of the nervous system which have innumerable peripheral nerves and arterial and venous bodies in close proximity. In spite of these complexities, the spine is a highly flexible structure, capable of a high degree of curvature and twist through a wide range of motion. The intervertebral discs provide mechanical cushion between adjacent vertebrae. Genetic or developmental irregularities, trauma, chronic stress, tumours, and disease, however, can result in spinal pathologies which either limit this range of motion, or which threaten the critical elements of the nervous system housed within the spinal column. A variety of systems have been disclosed in the art which achieve immobilization by implanting artificial assemblies in or on the spinal column.
In order to treat certain injuries or conditions of the spinal column an intervertebral device may be placed in the intervertebral disc space to fuse or promote fusion of adjacent vertebrae. Such fusion devices are often used in combination with stabilisation systems wherein a metal rod that is bendable to match the natural curvature of the spine is mechanically attached at strategically selected vertebrae, allowing the rod to be rigidly fixed to the spine. This provides a rigid support to the spinal column. For this, screws located in the bone structure are typically fixed to a specially designed clamp to attach to a spinal rod. A problem with these stabilisation systems if used in the cervical spine of small animals is that the space in this area is very limited and the quality of the underlying bone section is such that it is very difficult to achieve good fixation using cortical bone screws. There is the additional risk of screws being close to or damaging the nerves that are very close to the bone. A safer implant placement can be achieved from the ventral side where there is more bone structure for cortical screw placement. A fusion system that can be used in small animals, in particular for a ventral approach is needed, wherein confined spaces make conventional rod anchoring systems unsuitable.